PRNP and argyrophilic grain disease: Except for one subject, and irrespective of the expression of AD-related changes or hyperphosphorylated tau protein deposits in the form of primary age-related tauopathy (PART) and argyrophilic grain disease (AGD), there was generally no co-aggregation with hyperphosphorylated protein tau or ubiquitin in areas where PrP plaques were observed.